This invention relates to color display devices, and more particularly to means therein for securing hues of changing saturation.

In color displaygtdevices of known types, it is possible to secure multi-color variation by interposing designs of specific material between a pair of polarizing sheets located in front of a light source and by rotating one of the sheets in its plane while viewing the design.

An object of the invention is to provide color devices in which it is possible to secure as a result to the observer, views of specific hues whose saturation varies without change in hue.

Another object of the invention is to provide means whereby the change in hue saturation is accomplished periodically with the optical result of apparent flow from one point to another in a plane surface.

Still another object of the invention is to provide means for securing variation in hue saturation in plan surfaces.

Another object of the invention is to provide simple means for securing the foregoing which may be manufactured quickly at low cost.

To the accomplishment of the foregoing and such other objects as may hereinafter appear, the invention consists in the novel construction and arrangement of parts hereinafter to be described and then sought to be defined in the appended claims, reference being had to the accompanying drawing forming a part hereof, which shows merely for the purposes of illustrative disclosure, preferred embodiments of the invention, it being expressly understood, however, that changes may be made in practice within the scope of the appended claims without digressing from the inventive idea.

In the drawing:

Fig. 1 is a diagrammatic perspective view of one form of the invention;

Fig. 2 is an elevational view of the hue saturation varying .element of the device of Fig. 1;

Fig. 3 is a diagrammatic sectional view of a device adapted to effect variation in hue saturation;

Fig. 4 is a rear view of the device of Fig. 3 taken in front of the light source and viewed toward the right of Fig. 3; and

Fig. 5 is an elevational view of a modified form of hue saturation varying means.

Referring to the drawing l0 denotes a sheet of translucent isotropic material such as matte cellulose acetate or thermoplastic vinyl resins or any other non-polarizing translucent material. A sheet ll of polarizing material is secured to or located in front of the sheet I 0. Preferably the sheets l0 and H are secured together by an isotropic translucent cementitious material as liquid cellulose acetate or thermoplastic vinyl resins or the like. They may, however, be separate, or sheet Ill may be eliminated if the sheet II is translucent.

A second sheet I2 of matte cellulose acetate or other non-polarizing material is provided and positioned to lie in front of the sheet H- Areas I, II, III and IV of one face of this sheet have applied thereto non-polarizing transparent or translucent filters such as paints R, B, G, and O of different colors or hues. In the alternative color filters of isotropic material tinted to de-' sired color may be applied to sheet l2. As shown herein the sheet I2 is circular and each of th zones or areas I, II, III and IV constitutes substantially a quadrant of the circule. The nonpolarizing colored filter applied in quadrant I is, for example, red, that in quadrant II, blue, that in quadrant III, green, and that in quadrant IV, orange. Any other colors may be used and any other zoning division of the surface of sheet I! may be made. The important factor is that each area or zone has a transparent non-polarizing paint or other color filter of a specifically chosen color applied to it or that other means for transmitting polarized light of a specific hue through each zone be provided. One or more areas or zones I, II, III or IV may be provided.

The other face of sheet I! is subdivided into one or more areas or zones Ia, IIa, IIIa, IVa corresponding in shapes and number with the similar zones or areas in its first named face and positioned to lie in alignment therewith. Each zone in turn is subdivided into sections and each section has birefringent material 13 applied thereto. The birefringent material consists preferably of regenerated cellulose tape. Such tape is regenerated cellulose with a pressure sensitive isotropic adhesive on one surface. In such regenerated cellulose tape the direction of vibrations in the two rays arising from a normally incident beam are substantially parallel and perpendicular to the edge of the mill roll. The regenerated cellulose being birefringent has a. so-called signficant axis or direction." This refers to the projection onto its surface of the direction of vibration of the light of that one of the two rays which is propagated most rapidly. Over the area Ia of sheet l2 corresponding to the area I on its opposite face and in the successively adjacent sections of that area the strips l3 of birefringent material such as regenerated cellulose tape are applied. The angles of orientation of the significant axes or directions of the strip 13 ar progressively and preferably regularly different. For example, a

progressive variation of 10 in angles of orientation of the significant axes or directions of the strips applied in successive sections of the area Ia. may be used. The arrows in Fig. 2 denote diagrammatically the respective significant axes or directions and their progressive change or variation in 10 steps from to 90. This 10 variation, however, is merely exemplary as other desired angles of progression or variation may be selected. In the embodiment shown the uppermost strip in zone Ia has its significant axis at 10 with the horizontal, the next section at 20 therewith and so on through to 90 for the last of the strips in the zone In. in the clockwise direction.

Similarly the strips 13 of birefringent material in zone IIa are oriented at successively increasin angles of 10 in the clockwise direction as are those in zones 111a and Wu.

The particular shape of the strips or elements l3 can be anything desired. They may have the petal like radially, extending form shown in Fig. 2. As an alternative, strips or elements Ila may be arranged as shown in Fig. 5. Therein strips l3a in zone II) are all horizontal and successive strips progressively from top to bottom range in angles of orientation of their significant axes from 10 to 90". In zone 11112 the arrangement is opposite. In zones IIb and Nb the angles of orientation of the significant axes of the uppermost strips |3B are respectively horizontal and at 100 therewith and the angle of orientation of successive strips in the downward direction changes by 10 to the lowermost strips whose angle of orientation with the horizontal are respectively 10 and 180 for their significant axes. One or more layers of the birefringent material may be used in each strip location.

A great number of varieties of combinations may be provided in the shapes and number of the zones, the shapes of strips or elements in each zone, and in the direction of change in angular orientation of adjacent strips in each section. The principal factor is that in each zone of sheet 12 corresponding to a color zone provided on the other face of sheet 12, there should be sections of birefringent material arranged side by side having progressively different angles of orientation of their significant axes. The sheet l0 and color filters R, B, G and 0" could be replaced by other means for delivering polarized light of specific hue to each of the zones Ia, IIa, IIIa,,IVa, etc., of sheet l2 if desired.

Shrinkage of the birefringent strips II or 13a which would leave gaps between adjacent strips that would produce disturbing effects can be prevented by laminating a coating of isotropic material such as thermoplastic vinyl resins, cellulose acetate or other isotropic material over the strips to seal them from atmosphere.

A sheet I of polarizing material is positioned to lie in front of the sheet I2. This polarizing sheet, called an analyzer, is arranged to be fixed in its plane.

The sheets in and II are supported for rotation in their planes. They, for example, are supported in a frame IS. The latter is carried by grooved rollers l6, l1 and i8 arranged about its periphery. One of these rollers, for example I6, is driven in conventional manner So that the frame l rotates and consequently rotates polarizing sheet 14 in its own plane. The birefringent strips preferably lie on the face of sheet I2 nearest sheet Il.

As a result, the beams of light from the light source L traversing the first polarizing sheet II, the sheets l2 or l2a carrying the birefringent strips I! or Ba, and the second polarizing sheet or analyzer l4 reach the eye E as polarized light. The particular colors imparted to the zones I, II, III, IV, by the isotropic filters or paint in these zones on sheet I! are visible to the eye of the observer. However, as the polarizing sheet II is rotated the changing angle of polarization of that sheet relative to the fixed angle of polarization of polarizing sheet [4' together with the progressive changes in angle of orientation of the birefringent strips in each zone results in a novel optical eflect which primarily is a progressive variation in color saturation in each zone. In other words, the dominant color of each zone seen by the eye remains that imparted by the filter or paint, in the particular zone of sheet II.

However, the saturation of that color progressively waxes and wanes as the polarizing sheet II is rotated without any color change in the zone. This novel effect gives an illusion of motion and results in an attractive color display device. It can be utilized with other optical effects if desired.

The novel effect described will be substantially the same if the light source and the eye positions are interchanged, or if the analyzer sheet I4 is rotated instead of rotating polarizing sheet H. In other words, it is immaterial which one of the two polarizing sheets II or H is rotated. Likewise, if desired, sheet I! can be eliminated and the birefringent elements or strips I 3 or a can be applied directly to the polarizing sheet H or to the polarizing sheet H to lie between these two sheets. If this is done these strips are arranged upon either of these polarizing sheets in exactly the same manner as their arrangement upon sheet II. In such event, the color filters R, B, G and 0 preferably should be translucent. and .be applied to sheet H directly below the strips II.

While specific embodiments of the invention have been disclosed, it is to be understood that combinations embodying the features herein disclosed are possible in great numbers and varieties and are contemplated. There is no intention of limitation to the exact details shown and described.

What is claimed is:

1. A device of the character described for producing the optical effect of changing color sat.- uration in a zone of specific color as viewed by an observer upon its interposition between a light polarizer and a light analyzer one of which is rotatable in its plane comprising an isotropic sheet, a color filter of a chosen specific color applied directly to a zone of said sheet, and a plurality of strips of birefringent material applied side by side to said isotropic sheet in said zone and substantially coextensively with the color fil ter, said birefringent strips having uniform progressively different angles of orientation of their significant axes, whereby light transmitted through the sheet, color filter and strips from a light source behind the polarizer to the observer in front of the analyzer always has a specific hue in the zone of the chosen specific color of the filter, the saturation of said hue, however, varying progressively in said zone as either the polarizer or analyzer is rotated in its plane.

2. A device of the character described for producing the optical efiect of changing color saturation in a zone of specific color as viewed by an observer upon its interposition between a light polarizer and a light analyzer one of which is SEARCH R001! rotatable in its plane comprising a substantially isotropic sheet of light transmitting material, a substantially isotropic paint of chosen specific hue applied to a zone of said sheet, and a plurality of strips of birefringent material permanently applied side by side to said sheet in said zone and substantially coextensively with said paint in said zone, said birefringent strips having substantially uniform width, each strip having the same significant axis of birefringence in its length, said birefringent strips having uniform progressively difierent angles of orientation of their significant axes, whereby light transmitted through the sheet, paint and strips from a light source behind the polarizer to the observer in front of the analyzer appears to said observer in the said zone at all times to have the specific hue of said paint, the saturation of said hue, however, varying progressively in the zone as either the polarizer or analyzer is rotated in its plane.

FFORD BURCHELL.

6 REFERENCES CITED The following referenices are of record in the file of this patent: